OLED displays are made up of 12 to 15 layers of materials. In each pixel the red, green, and blue light-emitting materials are positioned side by side and sandwiched between materials that bring electrical current in and out of the device and that allow light to leave it. When these layers blend together during printing, device performance suffers.

DuPont has addressed this problem by using active molecules in the inks used to print each layer that are insoluble in the inks used to print the adjacent layers. This is more complex than it may sound, says Feehery. "Each of these materials is a major development effort on its own, and having to tie it to the ones above and below it imposes a lot of constraints," he says.

The company worked with Dainippon Screen to develop a multi-nozzle printer for the new inks. "The Dainippon printer works like a garden hose," says Feehery. It generates a continuous stream of ink, rather than droplets, and moves over a surface at rates of four to five meters per second while patterning a display. DuPont says that its red, green, and blue OLED materials can make displays that will last 15 years

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